1. Field of the Invention
The present invention relates to an optical modulator.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2011-112873 (Patent literature 1) discloses a multi-level optical phase modulator. Japanese Unexamined Patent Application Publication No. 7-049473 (Patent literature 2) discloses a Mach-Zehnder (MZ) optical modulator that provides modulated light with a high extinction ratio.
The multi-level optical phase modulator in Patent literature 1 includes a light intensity adjuster disposed between a phase modulation portion of a MZ optical modulator and an optical branching unit. The light intensity adjuster includes a gain medium and adjusts the intensity of input light to a predetermined intensity by means of the gain saturation characteristics of the gain medium.